Enamel containing barium and strontium compounds and for the enamelling of metals



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llo thawing. application med May a?, i927", Serial No. 194,862, and in France June 26, 19%.

The enamels in current use for the enamelling'o' metals by the known methods employed in this industry, i. e. by the application oit the enamel by sprinkling. rolling,

@n dipping, or in liquid form are essentially based upon lead compounds such as litharge, minium, massicot, lead carbonate, or zinc compounds, such as have been employed for a long period in `French and foreign enamel werl's.

The present invention relates to opaque enels both White and coloured, and chiefly to nsparent enamels of all colours socalled ceramic enamels upon cast and sheet iron and like other metals and it possesses a great ad vantage 'from 'the actvthart eliminates the pernicious elfects oit lea-d poisoning in the namel Works, as Well as the dcritrilication eels contai,ningn a ,L ounds, this taking r it Vaismelling process ,or during the use of heates 'with such enamels. amels :tree 'trom lead which are manaccerding method hereinaiter specified, are moet adyantageousrom that even after a long period they are not subject to the changes inherent in the lnaorrn enamels under the action ot the atmosphere. A rllhe different methodaoit enamelling are too well known to require anydetailed de-- scril ien. rilhe use or the enamels in accord ance with' the invention `will offer no changes in such methods. 'lWith reference for esample to cast iron according to the process in which the enamel. is applied as powder, the substance is directly sprinkled upon the ob ject which is suiiiciently clean and is heated the proper redness. ln the case of transparent enamelling on what is termed the ceramic process, layer ol White enamel must tir-st be put en in order "to form 'the background, and this is at once "followed by a second sprinkling' a' ransparent colored cnaniel with placinf the ohject .ag .a in the felation essentially consist ts such as barium and es which vary according to the composition in use, in all their natural or artilicial compounds or derivatives; by the use of barium or strontium lI am chielly enabled to obtain fluxes of a stable character, i. e. such as will preserve a perfect transparency during the different furnace heating operations required in the manufacture.

For the preparation of such enamels, either transparentA or opaque, and o tionally coloured, l may employ the following substances which are in current use:

Boric anhydride; which is furnished by berate of soda, optionally crystallized, or pandermite, borocalcite, borie acid or the like.

Sodium or potassium; in the form of carbonate, nitrates or chlorides.

Calcium; in the form of sulphate, carbonate, phosphate and the like, this constituent is moreover not necessary.

Silica; in the form of quartz, sands, silica of pebbles either natural or baked.

Fluorine; in its natural or artificial compounds. i

Alumina; represented by natural minerals.

Zinc; in the form of its usual compounds.

To such substances I usually add, according to-the invention, barium and eventually strontium in all their forms and natural or artificial derivatives such as carbonates, sulphates, chlorides, nitrates, phosphates, and the like. In these various compositions, l prefer to employ the silica in the form of feldspar and to ,directly add, as a surplus, alumina either hydrated or calcined.

All these substances, which are accurately proportioned and are intimately mixed, are then melted and cast in the dry or moist state, and are then ground up in the dry or moist state, according to the use Which is to be made of the enamel.

The composition of the mixtures may bviously vary according to a great number of formulae and Within very Wide limits, and l may mention the following:

Per cent Boris anhydride to 3() Barium 5 to 75 Strontum 5 to T5 Mlmlics 5 to im Silica" 5 to 40 Zinc l) to .20 LimoY 1 t0 50 Alumina 0,5 to 1G Fluorine 0,5 to 14 The compositions are coloured before or after they are melted, accordin to the nature of the product to be obtained, y adding the known colouring oxides such as the oxides of iron, manganese, copper, zinc, cadmium, uranium or the like.

To obtain opaque enamels with these different composltions, it is necessary to employ natural phosphate or sulphate of lime, or calcined bone phosphate, Vienna lime, phosphate of baryta, oxide of antimony of .the maximum purity in order to avoid prejudicial salts, oxide of tin, fiuorspar, cryolite and other bodies.

The following is an example of a white opaque enamel which has a remarkable solidity and adhesion, which may be employed directly upon cast iron, sheet iron, copper or the like, either alone and in powdered form for sanitary articles, Washstands, sinks, bathtubs and the like, or in liquid form, or as a first layer and a backing for a transparent coloured enamel:

This white opaque enamel may be used as a base for all opaque coloured enamels by adding the known colouring oxides.

The followinr is a formula for a transparent enamel o? the ceramic type:

Per cent Iiornx 1 Boi-ic acid 11,25 luryta 25 Feldspar 8,75 Alknles 11 Lime 11,5 Zinc 10 Alumina 1,5

This base and the bases of similar composition are coloured by adding suitable colouring substances, either before or after they are melted.

When applied upon a first layer of opaque white, this enamel can be favourably compared with the products in current use as concerns solidity, adhesion, brilliancy and other qualities. It can especially be subjected to a second or third heating in the muilie Without any change in its nature. lVhen the various enamels are to be applied upon sheet iron, I simply add to vthe enamels themselves the usual substances which will hold them in suspension in the liquid, such as pipe clay, kaolin, magnesia and the like.

Having thus described my process, What I claim as new therein, and my own invention, is:

A composition for enamelling metals by sprinkling upon a first coating of opaque white enamel, the use of a transparent or translucent enamel free from lead, essentially consisting in a mixture of borax 21%, boric acid 11.25%, baryta 25%, feldspar 8.75%, alkalies 11%, lime 11.5%, zinc 10%, alumina 1.5%.

In testimony whereof I have hereunto affixed my signature.

LOUIS ERNEST MIGEOT.

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